*Globodera rostochiensis *Population Density Effect on Potato Growth and Yield. Regression Models Estimation

S. MANEVA and Zl. TRIFONOVA

*“N. Poushkarov” Institute of Soil Science, Agrotechnology and Plant Protection, Department of Plant Protection, BG -2230 Kostinbrod, Bulgaria*

### Abstract

MANEVA, S. and Zl. TRIFONOVA, 2015. *Globodera rostochiensis *population density effect on potato growth and yield. Regression models estimation. *Bulg. J. Agric. Sci.*, 21: 815–821

Effect of initial population densities (Pi) of Bulgarian population of *Globodera rostochiensis *on the population dynamics and potato plants growth and yield was investigated in glasshouse and estimated using mathematical models. Potato cv. Nadejda seedlings were inoculated with Pi levels of 0, 0.1, 0.2, 0.5, 1, 2, 4, 8, 16, 32, 64 or 128 second stage juveniles/cm3 soil. The relation between Pi and final population density (Pf) was linear and DWLS regression described the relation of nematode reproductive index (Ri) and Pi. The linear regression with lg(X+I) transformation has been used to model the Pi and Pf effect on both, potato height and yield. Tolerance limit of potato to *G. rostochiensis *was between 0.5 and 1 juveniles/cm^{3} soil. The reduction of yield was significant different at 1.0 Pi. The model predicted that 4.0 Pi caused 50% yield loss and the maximal yield suppression of 87.6% occurred at 128 Pi. Maximum Ri of 27.0 occurred at 4.0 Pi, suggesting an interspecies competition.

*Key words: G. rostochiensis*, population density, potato growth, yield loss, mathematical model